Motive fluids for external combustion engines

ABSTRACT

A new class of motive fluids for external combustion engines characterized by a thermo-dynamic property which render them superior to water in external combustion engines.

United States Patent Somekh 1 1 Jan. 30, 1973 [54] MOTIVE FLUIDS FOREXTERNAL [56l References Cited COMBUSTlON'ENGINES UNITED STATES PATENTS[75] Inventor: George S. Somekh, New Rochelle,

NY. 3,282,048 l1/l966 Murphy etal. ..60/36 3,516,246 61970 M E ..6O [73]Ass1gnee: Union Carbide Corp., New York, I c /36 Primary Examiner-EdgarW. Geoghegan Filedi March 1971 Assistant Examiner-A. M. Ostrager [21] ppNOJ 123,434 Attorney-Paul A. Rose, John Aldo Cozzi and Bernard FrancisCrowe Related U.S. Application Data ABSTRACT [63] Continuation-in-partof Ser. No. 862,526, Sept. 30, v

1969, abandoned. A new class of motive fluids for external combusuonengines characterized by a thermo-dynamic property 52 U.S. c1 ..60/36,252/67 which render them SW?rior Water in external 511 1m. (:1 ..F0lk25/00 engmes- [58] Field of Search ..60/36; 252/67 19 Claims, N0Drawings MOTIVE FLUIDS FOR EXTERNAL COMBUSTION ENGINES This is acontinuation-in-part of Ser. No. 862,526 filed Sept. 30, 1969, nowabandoned.

This invention relates to the production of mechanical or electricalpower using new power fluids.

In one respect the invention relates to new motive fluids for externallyheated engine systems.

In another aspect, the invention relates to motive fluids and powersystems using all types of engines (such as, for example, turbines, orreciprocating engines) as the prime mover in the power system, whichutilize a vapor-liquid engine cycle.

Due to its extremely low cost and ready availability, water has beenused as the power fluid in a vast majority of such systems. However,because of its low molecular weight, water has proven to be relativelyinefficient for it requires practically small engines and/or turbineblades. Efficiency is also lowered in the conventional power cyclebecause of the high freezing point of water and its low vapor pressuresnear freezing point. The turbine is also subject to erosion of theturbine blades resulting from excessive liquid formation in the turbineunder working fluid. The ordinary expedient to minimize the liquidformation is to utilize one or more re-heat cycles which increases thecost of the system.

Thus it would be advantageous to utilize the fluids which do not possessdisadvantages of water in externally heated engine systems, and whichcan be utilized in both large-scales and small-scale systems.

It has now been found that a group of compounds, more fully describedherein, possess one or more properties that are superior to those ofwater for use in power cycles. These systems are also characterized bythe ability to be used in systems having lower investment costs andsystems which use water, and yet these compounds are also capable ofhigher efficiency than a water system.

It has further been found that the fluids of the instant invention canbe used in binary fluid systems while avoiding excessively high and lowpressures.

The fluids of the instant invention can be used in a variety of powergeneration devices, such as centralstation, power plants,central-station nuclear power plants, gas powered air conditioners,space vehicles, heating/electric power systems for homes and buildings,industrial waste heat recovery systems, and self-propelled vehicles ofall types including automobiles, boats, ships and railroads.

The power fluids of the instant invention are phosphorous halides,titanium halides, silicon halides, fluorinated cyclic amines, tetraalkylsilanes having from 1 to about four carbon atoms'in the alkyl groups andalkyl halosilanes containing from one to about eight carbon atoms in thealkyl groups.

Representative phosphorous halides include and the like.

Representative titanium halides include; titanium tetrachloride,titanium tetrabromide, titanium tetrafluoride, dichlorodibromo titaniumand the like.

Representative silicon halides include; silicon tetrachloride, trichlorosilane, dibromochloro silane,

iodo trichlorosilane, silicon tetrabromide, dichlorodiiodo silane, andthe like.

The preferred tetraalkyl silanes include tetramethyl silane andtetraethyl silane, although tetrapropyl silane, tetraisopropyl silane,and the like can also be used if desired.

Representative alkyl halosilanes include methyltrichlorosilane,trimethylchloro silane, trimethylfluoro silane, ethyltrichloro silane,diethyldifluoro silane, methyldichloro silane, trichloromethyl silane,and the like.

The following compilation represents some specific examples andthermodynamic properties of the motive fluids of the instant invention:

Molecular Boiling Freezing Critical Max. use

Weight Point Point Temp. Temp. Compound C "C "C C PCl 137.3 75.5 1 12290.0 300 PBr 270.7 172.9 40 458.1 PFCI, 120.8 13.85 l44.0 189.8 SiCl169.9 57.6 233 800 SiCl,H 135.5 31.8 128.2 206.0 500 SiBr,Cl, 258.8104.4 45.5 318.9 400 SiCl l 261.4 113.5 60 321.7 400 TiCl, 189.7 136.425 370 l000 TiBr, 367.5 233.4 39.0 537 1000 (CH Si 88.2 27.0 102.1 550(C,H,),Si 144.3 153.0 82.5 400 CH,Cl,Si 149.5 65.7 77.5 400 (Cl-1,);C1Si57.9 57.7 400 (Cl-1,),FSi 16.4 74.3 400 C,l-l Cl,Si 163.5 99.5 105.6 400(C,1-l,),F,Si 58.0 400 CH,Cl,HSi 1 15.0 42.3 93 198 400 C F N 169.1 83.341.5 600 C,F N, 152.1 600 The comparable properties of water are asfollows:

A particularly important advantage of the motive fluids of the instantinvention is that they can be employed in power systems forself-propelled vehicles and do not give off large amounts of wasteproducts which would further contaminate the polluted air surroundingmany of our metropolitan areas today. The heating plants for suchsystems emit a substantially lower amount of pollutants to the air.External combustion engines can employ more air and longer burning timesthan the conventional internal combustion engines used today, thuspermitting a much cleaner exhaust.

Presently, extensive research is being conducted to find alternatives tothe internal combustion engine. Turbine powered automobiles using steamas the motive fluid are being investigated for feasibility byrepresentatives of the automotive industry. Other companies have beenlooking into the use of fluorocarbons as the motive fluid in turbineengines. The steam and fluorocarbons of these systems can be replacedwith the'fluids of the instant invention and thus be able to utilize thesuperior properties of the motive fluids of the instant invention.

Much research is also being conducted today for operational powersystems in space vehicles. Here, the size of the power system is aprimary consideration. The smaller engine sizes permissible when theinstant motive fluids are utilized as well as the high efficienciesavailable from such fluids makes such utilization particularlyadvantageous for space vehicles.

The standard external combustion engine system is composed of a boilerto convert the motive fluid from a liquid to vapor and thus impartingworking energy, a prime mover to operate from the working energy in themotive fluid, and a condenser to reconvert the spent vapor back intoliquid form. The boiler can be heated in a number of ways including butnot limited to the burning of conventional fuels and nuclear power. Theprime mover can be a turbine engine or a reciprocating piston engine. Ina binary cycle, the condenser can be a heat exchanger wherein thehigh-temperature fluid is converted from vapor back to liquid and thelow-temperature fluid picks up additional heat energy from thistransformation. Ordinarily, the condenser is water or air cooled.

A high-temperature fluid is one when employed in a binary cyclepossesses a boiling point higher than the other fluid in the cycle. Inlike manner, a low-temperature fluid of a binary cycle is that onehaving a lower boiling point than the other fluid of the cycle. Noprecise standards can be given for the terms are relative.

A binary cycle can be successfully carried out by using one fluid forthe high-temperature end of a power cycle and another fluid for thelow-temperature end. Thus, a plurality of prime movers, i.e., turbinesor reciprocating engines, can be utilized in the same system. Here, thehigh-temperature fluid, after passing through a turbine section in anexpanded state, is condensed by countercurrent heat exchange with thecompanion low-temperature fluid. This fluid goes through a secondturbine section, then is condensed with water and pumped back to theheating unit.

The heating unit in these systems can be a low grade gas combustionoperation such as combustion from natural gas. It can also be a nuclearheating unit. The function of the heating unit is to transfer heat tothe working fluids to enable them to activate the prime mover.

A binary cycle can use both a high-temperature fluid and alow-temperature fluid of the present invention. Alternatively, such acycle can use one fluid of the present invention, either ahigh-temperature or a lowtemperature fluid, and another fluid for theother end of the cycle. For example, titanium tetrachloride (TiCl afluid of the present invention) can be used for the high-temperature endof the cycle and a fluorocarbon such as difluorodichloromethane can beused as the low-temperature fluid. A reverse example is the utilizationof water as the high-temperature fluid and tetramethyl silane, a fluidof the present invention, as the low-temperature fluid.

Contemplated within the scope of the present invention is theutilization of one or two fluids of the present invention in combinationpower generation/air conditioning and heating systems. In a gas poweredair conditioner, heat supplied from the combustion of natural gas istransferred to a power fluid, which in turn is expanded through aturbine that drives the compressor of a refrigeration cycle.

Such a system can be operated by combinations of the known fluids andthe fluids of the present invention. Obviously, the fluids to be used asrefrigerants selected from those of the present invention must be thelowboiling ones.

Titanium tetrachloride can be used as the power fluid and a commercialfluorocarbon refrigerant can be used as the refrigeration fluid.

At times, it may be more practical to use a single fluid for both thepower and refrigeration cycles. This does, of course, mean a compromiseof the fluids properties. For example, tetramethyl silane, which islower boiling than an optimum power fluid and higher-boiling than anoptimum refrigerant, can be used as the single fluid.

A particularly useful fluid of the present invention is titaniumtetrachloride (TiCl Its critical temperature (370C) is very near-that ofwater (374.4C), yet the saturated vapor pressure at elevatedtemperatures is considerably lower with TiCl, than with water. While thevapor pressure of water at 300C is 64,000 mm Hg, the vapor pressure ofTiCl, at the same temperature is merely 18,000 mm Hg. Furthermore, TiCl,has a substantially lower freezing point (25C) than water (0C).

A temperature-entropy diagram for TiCl, reveals that the relatively lowheat capacity of the fluid results in a rather steep saturated liquidcurve, which in turn yields greater efficiency. The saturated vaporcurve is nearly vertical so that expansion of saturated or superheatedvapor would tend not to result in liquid formation in the expander.Thus, reheat cyclesand the associated complexity and increasedinvestment costswould not be needed.

Another fluid is phosphorous trichloride (PCI I which has a considerablyhigher vapor pressure than water at 50C (330 mm Hg vs. 93 mm Hg) so thatexpansion down to low temperatures would result in the need for enginesof considerably smaller sizes with PC]; than with water. Yet, at highertemperatures the vapor pressures of PC]; are actually lower than thoseof water. For example, at 280C the vapor pressure of PCl is 35,000 mmHg, whereas that of water is 45,000 mm Hg. Furthermore, PCl has afreezing point of -l 12C.

Analysis of a PC] temperature-entropy diagram indicates that thesaturated vapor curve becomes more vertical as the temperature isreduced, whereas a temperature-entropy diagram for water shows that thesaturated vapor curve becomes more horizontal as the temperature isreduced. Thus, PCl can be used in supercritical cycles whereby little orno liquid is obtained in the engine when the fluid is expanded down tolow temperatures (i.e., 25C).

Another fluid of the instant invention is dibromodichlorosilane(SiBr,Cl,) for it can be used at a higher temperature range than PClThis fluid also has vapor pressures that, compared to water, are lowerat high temperatures and higher at low temperatures. It has a moderateboiling point (l04.4C) and low freezing point (-45.5C).

the temperature-entropy diagram of SiBr,Cl, shows a nearly verticalsaturated vapor curve. The high slope is suitable for the expansion ofboth super-critical and slightly super-heated vapors at moderately hightemperatures.

It is emphasized that the invention resides, not in any particular powersystem or apparatus, but rather in a new class of power fluids which canbe employed in a system having an external combustion engine as itsdriving force, such as a turbine or reciprocating piston engine. Thesystem is enhanced by full utilization of the properties of the instantpower fluids rather than by any manipulation or readjustment of theequipment used to produce electrical or mechanical power.

The motive fluids of this invention are uniquely adapted to impartingworking energy and internal combustion engines in their conversion fromliquid to vapor and then utilizing the working energy of said vapor tooperate a prime mover.

What is claimed is:

l. A method of imparting working energy in an external combustion systemwhich comprises converting a motive fluid selected from the classconsisting of titanium halides, phosphorous halides, silicon halides,tetraalkyl silanes wherein the alkyl group contain from about one tofour carbon atoms, and alkyl halosilanes wherein the alkyl groupscontain one to about eight carbon atoms from liquid to vapor andutilizing the working energy of said vapor to operate a prime mover.

2. Method claimed in claim 1 wherein the motive fluid is a titaniumhalide.

3. Method claimed in claim 2 wherein the titanium halide is titaniumtetrachloride.

4. Method claimed in claim 1 wherein the motive fluid is a phosphoroushalide.

5. Method claimed in claim 4 wherein the phosphorous halide isphosphorous trichloride.

6. Method claimed in claim 1 wherein the motive fluid is a siliconhalide.

7. Method claimed in claim 6 wherein the silicon halide isdibromodichlorosilane.

8. Method claimed in claim 6 wherein the silicon halide istetrachlorosilane.

9. Method claimed in claim 6 wherein the silicon halide istrichlorosilane.

10. Method claimed in claim 1 wherein the motive fluid is a tetraalkylsilane.

11. Method claimed in claim 10 wherein the tetraalkyl silane istetramethylsilane.

12. Method claimed in claim 10 wherein the tetraalkyl silane istetraethylsilane.

13. Method claimed in claim 1 wherein the motive fluid is analkylhalosilane.

14. Method claimed in claim 13 wherein the motive fluid alkylhalosilaneis methyltrichloro silane.

15. Method claimed in claim 13 wherein the alkylhalosilane istrimethylchloro silane.

16. Method claimed in claim 13 wherein the alkylhalosilane istrimethylfluoro silane.

17. Method claimed in claim 13 wherein the alkylhalosilane isethyltrichloro silane.

18. Method claimed in claim 13 wherein the alkylhalosilane isdiethyldifluoro silane.

19. Method claimed in claim 13 wherein the alkylhalosilane is methyldichlorosilane.

1. A method of imparting working energy in an external combustion systemwhich comprises converting a motive fluid selected from the classconsisting of titanium halides, phosphorous halides, silicon halides,tetraalkyl silanes wherein the alkyl group contain from about one tofour carbon atoms, and alkyl halosilanes wherein the alkyl groupscontain one to about eight carbon atoms from liquid to vapor andutilizing the working energy of said vapor to operate a prime mover. 2.Method claimed in claim 1 wherein the motive fluid is a titAnium halide.3. Method claimed in claim 2 wherein the titanium halide is titaniumtetrachloride.
 4. Method claimed in claim 1 wherein the motive fluid isa phosphorous halide.
 5. Method claimed in claim 4 wherein thephosphorous halide is phosphorous trichloride.
 6. Method claimed inclaim 1 wherein the motive fluid is a silicon halide.
 7. Method claimedin claim 6 wherein the silicon halide is dibromodichlorosilane. 8.Method claimed in claim 6 wherein the silicon halide istetrachlorosilane.
 9. Method claimed in claim 6 wherein the siliconhalide is trichlorosilane.
 10. Method claimed in claim 1 wherein themotive fluid is a tetraalkyl silane.
 11. Method claimed in claim 10wherein the tetraalkyl silane is tetramethylsilane.
 12. Method claimedin claim 10 wherein the tetraalkyl silane is tetraethylsilane. 13.Method claimed in claim 1 wherein the motive fluid is analkylhalosilane.
 14. Method claimed in claim 13 wherein the motive fluidalkylhalosilane is methyltrichloro silane.
 15. Method claimed in claim13 wherein the alkylhalosilane is trimethylchloro silane.
 16. Methodclaimed in claim 13 wherein the alkylhalosilane is trimethylfluorosilane.
 17. Method claimed in claim 13 wherein the alkylhalosilane isethyltrichloro silane.
 18. Method claimed in claim 13 wherein thealkylhalosilane is diethyldifluoro silane.